Distinct neuropsychological profiles correspond to distribution of cortical thinning in inherited prion disease caused by insertional mutation

Personalized brain MRI revealed distinct functional and anatomical disruptions in Creutzfeldt-Jakob disease and Alzheimer's disease

AIMS

Creutzfeldt-Jakob disease (CJD) is a lethal neurodegenerative disorder, which leads to a rapidly progressive dementia. This study aimed to examine the cortical alterations in CJD, changes in these brain characteristics over time, and the differences between CJD and Alzheimer's disease (AD) that show similar clinical manifestations.

METHODS

To obtain reliable, subject-specific functional measures, we acquired 24 min of resting-state fMRI data from each subject. We applied an individual-based approach to characterize the functional brain organization of 10 patients with CJD, 8 matched patients with AD, and 8 normal controls. We measured cortical atrophy as well as disruption in resting-state functional connectivity (rsFC) and then investigated longitudinal brain changes in a subset of CJD patients.

RESULTS

CJD was associated with widespread cortical thinning and weakened rsFC. Compared with AD, CJD showed distinct atrophy patterns and greater disruptions in rsFC. Moreover, the longitudinal data demonstrated that the progressive cortical thinning and disruption in rsFC mainly affected the association rather than the primary cortex in CJD.

CONCLUSIONS

CJD shows unique anatomical and functional disruptions in the cerebral cortex, distinct from AD. Rapid progression of CJD affects both the cortical thickness and rsFC in the association cortex.

Selective vulnerability to atrophy in sporadic Creutzfeldt-Jakob disease

OBJECTIVE

Identification of brain regions susceptible to quantifiable atrophy in sporadic Creutzfeldt-Jakob disease (sCJD) should allow for improved understanding of disease pathophysiology and development of structural biomarkers that might be useful in future treatment trials. Although brain atrophy is not usually present by visual assessment of MRIs in sCJD, we assessed whether using voxel-based morphometry (VBM) can detect group-wise brain atrophy in sCJD.

METHODS

3T brain MRI data were analyzed with VBM in 22 sCJD participants and 26 age-matched controls. Analyses included relationships of regional brain volumes with major clinical variables and dichotomization of the cohort according to expected disease duration based on prion molecular classification (i.e., short-duration/Fast-progressors (MM1, MV1, and VV2) vs. long-duration/Slow-progressors (MV2, VV1, and MM2)). Structural equation modeling (SEM) was used to assess network-level interactions of atrophy between specific brain regions.

RESULTS

sCJD showed selective atrophy in cortical and subcortical regions overlapping with all but one region of the default mode network (DMN) and the insulae, thalami, and right occipital lobe. SEM showed that the effective connectivity model fit in sCJD but not controls. The presence of visual hallucinations correlated with right fusiform, bilateral thalami, and medial orbitofrontal atrophy. Interestingly, brain atrophy was present in both Fast- and Slow-progressors. Worse cognition was associated with bilateral mesial frontal, insular, temporal pole, thalamus, and cerebellum atrophy.

INTERPRETATION

Brain atrophy in sCJD preferentially affects specific cortical and subcortical regions, with an effective connectivity model showing strength and directionality between regions. Brain atrophy is present in Fast- and Slow-progressors, correlates with clinical findings, and is a potential biomarker in sCJD.

Prion disease diagnosis using subject-specific imaging biomarkers within a multi-kernel Gaussian process

Prion diseases are a group of rare neurodegenerative conditions characterised by a high rate of progression and highly heterogeneous phenotypes. Whilst the most common form of prion disease occurs sporadically (sporadic Creutzfeldt-Jakob disease, sCJD), other forms are caused by prion protein gene mutations, or exposure to prions in the diet or by medical procedures, such us surgeries. To date, there are no accurate quantitative imaging biomarkers that can be used to predict the future clinical diagnosis of a healthy subject, or to quantify the progression of symptoms over time. Besides, CJD is commonly mistaken for other forms of dementia. Due to the heterogeneity of phenotypes and the lack of a consistent geometrical pattern of disease progression, the approaches used to study other types of neurodegenerative diseases are not satisfactory to capture the progression of human form of prion disease. In this paper, using a tailored framework, we aim to classify and stratify patients with prion disease, according to the severity of their illness. The framework is initialised with the extraction of subject-specific imaging biomarkers. The extracted biomakers are then combined with genetic and demographic information within a Gaussian Process classifier, used to calculate the probability of a subject to be diagnosed with prion disease in the next year. We evaluate the effectiveness of the proposed method in a cohort of patients with inherited and sporadic forms of prion disease. The model has shown to be effective in the prediction of both inherited CJD (92% of accuracy) and sporadic CJD (95% of accuracy). However the model has shown to be less effective when used to stratify the different stages of the disease, in which the average accuracy is 85%, whilst the recall is 59%. Finally, our framework was extended as a differential diagnosis tool to identify both forms of CJD among another neurodegenerative disease. In summary we have developed a novel method for prion disease diagnosis and prediction of clinical onset using multiple sources of features, which may have use in other disorders with heterogeneous imaging features.

The language disorder of prion disease is characteristic of a dynamic aphasia and is rarely an isolated clinical feature

BACKGROUND

Akinetic mutism is a key diagnostic feature of prion diseases, however, their rapidly progressive nature makes detailed investigation of the language disorder in a large cohort extremely challenging. This study aims to position prion diseases in the nosology of language disorders and improve early clinical recognition.

METHODS

A systematic, prospective investigation of language disorders in a large cohort of patients diagnosed with prion diseases. 568 patients were included as a sub-study of the National Prion Monitoring Cohort. All patients had at least one assessment with the MRC Scale, a milestone-based functional scale with language and non-language components. Forty patients, with early symptoms and able to travel to the study site, were also administered a comprehensive battery of language tests (spontaneous speech, semantics, syntax, repetition, naming, comprehension and lexical retrieval under different conditions).

RESULTS

5/568 (0.9%) patients presented with leading language symptoms. Those with repeated measurements deteriorated at a slower rate in language compared to non-language milestones. Amongst the subgroup of 40 patients who underwent detailed language testing, only three tasks-semantic and phonemic fluency and sentence comprehension-were particularly vulnerable early in the disease. These tasks were highly correlated with performance on non-verbal executive tests. Patients were also impaired on a test of dynamic aphasia.

CONCLUSION

These results provide evidence that the language disorder in prion disease is rarely an isolated clinical or cognitive feature. The language abnormality is indicative of a dynamic aphasia in the context of a prominent dysexecutive syndrome, similar to that seen in patients with the degenerative movement disorder progressive supranuclear palsy (PSP).

Neuroanatomical correlates of prion disease progression - a 3T longitudinal voxel-based morphometry study

PURPOSE

MRI has become an essential tool for prion disease diagnosis. However there exist only a few serial MRI studies of prion patients, and these mostly used whole brain summary measures or region of interest based approaches. We present here the first longitudinal voxel-based morphometry (VBM) study in prion disease. The aim of this study was to systematically characterise progressive atrophy in patients with prion disease and identify whether atrophy in specific brain structures correlates with clinical assessment.

METHODS

Twenty-four prion disease patients with early stage disease (3 sporadic, 2 iatrogenic, 1 variant and 18 inherited CJD) and 25 controls were examined at 3T with a T1-weighted 3D MPRAGE sequence at multiple time-points (2-6 examinations per subject, interval range 0.1-3.2 years). Longitudinal VBM provided intra-subject and inter-subject image alignment, allowing voxel-wise comparison of progressive structural change. Clinical disease progression was assessed using the MRC Prion Disease Rating Scale. Firstly, in patients, we determined the brain regions where grey and white matter volume change between baseline and final examination correlated with the corresponding change in MRC Scale score. Secondly, in the 21/24 patients with interscan interval longer than 3 months, we identified regions where annualised rates of regional volume change in patients were different from rates in age-matched controls. Given the heterogeneity of the cohort, the regions identified reflect the common features of the different prion sub-types studied.

RESULTS

In the patients there were multiple regions where volume loss significantly correlated with decreased MRC scale, partially overlapping with anatomical regions where yearly rates of volume loss were significantly greater than controls. The key anatomical areas involved included: the basal ganglia and thalamus, pons and medulla, the hippocampal formation and the superior parietal lobules. There were no areas demonstrating volume loss significantly higher in controls than patients or negative correlation between volume and MRC Scale score.

CONCLUSIONS

Using 3T MRI and longitudinal VBM we have identified key anatomical regions of progressive volume loss which correlate with an established clinical disease severity index and are relevant to clinical deterioration. Localisation of the regions of progressive brain atrophy correlating most strongly with clinical decline may help to provide more targeted imaging endpoints for future clinical trials.

A comparison of FreeSurfer-generated data with and without manual intervention

This paper examined whether FreeSurfer-generated data differed between a fully-automated, unedited pipeline and an edited pipeline that included the application of control points to correct errors in white matter segmentation. In a sample of 30 individuals, we compared the summary statistics of surface area, white matter volumes, and cortical thickness derived from edited and unedited datasets for the 34 regions of interest (ROIs) that FreeSurfer (FS) generates. To determine whether applying control points would alter the detection of significant differences between patient and typical groups, effect sizes between edited and unedited conditions in individuals with the genetic disorder, 22q11.2 deletion syndrome (22q11DS) were compared to neurotypical controls. Analyses were conducted with data that were generated from both a 1.5 tesla and a 3 tesla scanner. For 1.5 tesla data, mean area, volume, and thickness measures did not differ significantly between edited and unedited regions, with the exception of rostral anterior cingulate thickness, lateral orbitofrontal white matter, superior parietal white matter, and precentral gyral thickness. Results were similar for surface area and white matter volumes generated from the 3 tesla scanner. For cortical thickness measures however, seven edited ROI measures, primarily in frontal and temporal regions, differed significantly from their unedited counterparts, and three additional ROI measures approached significance. Mean effect sizes for edited ROIs did not differ from most unedited ROIs for either 1.5 or 3 tesla data. Taken together, these results suggest that although the application of control points may increase the validity of intensity normalization and, ultimately, segmentation, it may not affect the final, extracted metrics that FS generates. Potential exceptions to and limitations of these conclusions are discussed.

Predictive testing for inherited prion disease: report of 22 years experience

The inherited prion diseases (IPD) are a group of untreatable neurodegenerative diseases that segregate as autosomal dominant traits. Mutations in the prion protein gene (PRNP) were first found to be causal of IPD in 1989, before the molecular genetic characterisation of any other neurodegenerative disease. Predictive testing for IPD has subsequently been carried out at a single UK clinical and research centre for 22 years. We have analysed the uptake, consequences and factors influencing the decision for predictive testing over this period. In all, 104 predictive tests were done on individuals at 50% risk, compared with 135 positive diagnostic tests. Using genealogies from clinical records, we estimated that 23% of those at 50% risk have completed testing. There was no gender bias, and unsurprisingly, there was a slight excess of normal results because some patients were already partly through the risk period because of their age. An unexpectedly large number of patients developed symptoms shortly after predictive testing, suggesting that undisclosed early symptoms of disease may prompt some patients to come forward for predictive testing. Fifteen per cent of predictive tests were done >10 years after molecular diagnosis in a proband. A strong determinant of the timing of testing in these patients was a second diagnosis in the family. IPD may generate infectious prions that might be transmitted by surgical procedures; however, we found no evidence that public health information influenced decisions about predictive testing.

Protease-sensitive prions with 144-bp insertion mutations

Insertion of 144-base pair (bp) containing six extra octapeptide repeats between residues 51 and 91 of prion protein (PrP) gene is associated with inherited prion diseases. Most cases linked to this insertion examined by Western blotting showed detectable proteinase K-resistant PrPSc (rPrPSc) resembling PrPSc type 1 and type 2 in sporadic Creutzfeldt-Jakob disease (sCJD), or PrP7-8 in Gerstmann-Sträussler-Scheinker disease. However, cases lacking detectable rPrPSc also have been reported. Which PrP conformer is associated with neuropathological changes in the cases without detectable rPrPSc remains to be determined. Here we report that while all six but one subjects with the 144-bp insertion mutations examined display the pathognomonic PrP patches in the cerebellum, one of them exhibits no detectable typical rPrPSc even in PrPSc-enriched preparations. Instead, a large amount of abnormal PrP is captured from this case by gene 5 protein and sodium phosphotungstate, reagents that have been proved to specifically capture abnormal PrP. All captured abnormal PrP from the cerebellum and other brain regions is virtually sensitive to PK-digestion (termed sPrPSc). The presence of the predominant sPrPSc but absence of rPrPSc in this 144-bp insertion-linked inherited CJD case suggests that mutant sPrPSc is the main component of the PrP deposit patches and sPrPSc is sufficient to cause neurotoxicity and prion disease.

The relationship between schizophrenia and frontotemporal dementia

Schizophrenia is a relatively common disorder diagnosed by the presentation of psychotic symptoms in the absence of identifiable neurologic or other organic cause. Frontotemporal dementia (FTD) is a relatively rare progressive neurodegenerative disorder that can present with a multitude of cognitive and behavioral symptoms including psychosis. At times, this phenotypic overlap can mean that schizophrenia and FTD are 2 possibilities in the differential diagnosis of a psychotic presentation. In this article, we systematically review the literature on the relationship between schizophrenia and FTD including case reports that highlight the potential for diagnostic confusion, clinical studies examining the relationship between the disorders, and the molecular evidence of shared pathophysiologic mechanisms. Although a relationship between the disorders is not definitively supported by the current literature, we identify the characteristics of a psychotic presentation that should alert the clinician to the possibility of FTD and describe the areas where further research is needed to clarify the pathophysiologic relationship.

Multiparameter MR imaging in the 6-OPRI variant of inherited prion disease

BACKGROUND AND PURPOSE

Inherited prion diseases represent over 15% of human prion cases and are a frequent cause of early onset dementia. The purpose of this study was to define the distribution of changes in cerebral volumetric and microstructural parenchymal tissues in a specific inherited human prion disease mutation combining VBM with VBA of cerebral MTR and MD.

MATERIALS AND METHODS

VBM and VBA of cerebral MTR and MD were performed in 16 healthy control participants and 9 patients with the 6-OPRI mutation. An analysis of covariance consisting of diagnostic grouping with age and total intracranial volume as covariates was performed.

RESULTS

On VBM, there was a significant reduction in gray matter volume in patients compared with control participants in the basal ganglia, perisylvian cortex, lingual gyrus, and precuneus. Significant MTR reduction and MD increases were more anatomically extensive than volume differences on VBM in the same cortical areas, but MTR and MD changes were not seen in the basal ganglia.

CONCLUSIONS

Gray matter and WM changes were seen in brain areas associated with motor and cognitive functions known to be impaired in patients with the 6-OPRI mutation. There were some differences in the anatomic distribution of MTR-VBA and MD-VBA changes compared with VBM, likely to reflect regional variations in the type and degree of the respective pathophysiologic substrates. Combined analysis of complementary multiparameter MR imaging data furthers our understanding of prion disease pathophysiology.